Flame retardant method

ABSTRACT

Mixtures comprising compounds of the formula ##STR1## wherein A is either NH 2  or N=P(NH 2 ) 3 , provided at least one A is N=P(NH 2 ) 3 , have been found to be good flame-retardants for material made from cotton or polyester-cotton having about 30 to 70% by weight cotton. Conveniently the material can be treated with an aqueous solution containing a sufficient amount of said mixtures and the material dried to make the material self extinguishing. Then the treated and dried material is cured at a sufficient temperature to bond said compounds to the material. Alternatively and usually preferably the drying and curing can be accomplished as a single operation. The treatment solution can additionally contain auxiliary treatment agents to make the material more durable to washing.

This is a division of application Ser. No. 490,607, filed July 22, 1974.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Fireproofing.

2. Description of the Prior Art

One of the older patents in this art is U.S. Pat. No. 2,782,133 teaching aminocyclophosphazene as a fireproofing agent for cellulosic fibers such as cotton. A recent patent is U.S. Pat. No. 3,711,542 teaching certain new N-methylol phosphazene compounds as flame retardants on cotton, and this patent under Background of the Invention contains a summary of certain phosphazene prior art on flameproofing.

SUMMARY OF THE INVENTION

Mixtures comprising compounds of the formula ##STR2## wherein A is either NH₂ or N=P(NH₂)₃, provided at least one A is N=P(NH₂)₃, have been found to be good flameretardants for material made from cotton or polyester-cotton having about 30 to 70% by weight cotton. Conveniently the material can be treated with an aqueous solution containing a sufficient amount of said mixtures and the material dried to make the material self extinguishing. Then the treated and dried material is cured at a sufficient temperature to bond said compounds to the materials. Alternatively and usually preferably the drying and curing can be accomplished as a single operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preparation of the Flame-Proofing Reagents

Melamine and phosphorus pentachloride were allowed to react in molar ratios of 1/3; 1/2; 1/1. After reaction with ammonia, three materials were obtained having different solubilities, although their infrared spectra were quite similar. Elemental analyses showed that these materials were not pure compounds nor were they the simple materials expected by the reaction of the trihalophosphazenes with excess ammonia. ##STR3##

A reference to the tris-trichlorophosphazene was found in the literature (1. Derkash, USSR 168,693, C.A. 63, 1700g; C.A. 69, 36082s); however, no reference to any of the ammoniated compounds from melamine +PCl₃ + NH has been found. All of the ammoniated products were water soluble and contained chlorine. Recrystallization from water resulted in losses of chlorine and significant changes in the phosphorus analyses. These products flame retarded cotton and 65/35 polyester-cotton.

The reaction of 3 moles of phosphorus pentachloride and a mole of melamine will be used to represent all of the reactions between these two reagents in varying stoichiometries. ##STR4##

A mixture of 30.0 g (0.24 m) of melamine (MCB) and 177.5 g (0.85 m) of PCl₅ with 200 ml of CHCl₃ was heated at gentle reflux with stirring, until the evolution of HCl had ceased (44 hours). The top of the condenser was protected by a Drierite tube. The mixture was allowed to cool, and the solvent and trapped HCl were removed on a rotary evaporator leaving 190.7 g of a white solid which smelled of CHCl₃. The solid was reactive to water but was not as reactive as PCl₅.

The solid was placed in a 3-liter flask with 500 ml of toluene. Eight hundred ml of liquid ammonia was added in portions. A Dry Ice condenser was used to contain the ammonia. This mixture was stirred overnight. The copious white solid that had formed was filtered to remove the toluene. Twelve hundred ml of ammonia was poured cautiously over the filter cake. The solid left on the filter and the solid left after evaporation of the ammonia from the filtrate had identical infrared spectra indicating the presence of both product and ammonium chloride and that the product was soluble in ammonia. The residue from evaporation of the ammonia filtrate was added to the filter cake giving a combined weight of product of 230 g. The product was soluble in water. The mixture was also soluble in methanol and ethanol and formed a salt with acetic acid. There was no apparent solubility in acetone, acetonitrile, THF, benzene, toluene, chloroform or methylene chloride.

The 230 g of solids product was slurried in 1200 ml of chloroform and 315 ml (3 m) of diethylamine. The mixture was heated slowly to reflux. (This method, see below, affords a chloroform soluble amine hydrochloride from the ammonium chloride, thus enabling separation of the phosphazene.)

    (C.sub.2 H.sub.5).sub.2 NH + NH.sub.4 Cl → (C.sub.2 H.sub.5).sub.2 NH.sub.2 Cl + NH.sub.3

the ammonia was detected at the top of the condenser. The mixture was refluxed overnight. The cooled solution was filtered to remove the red chloroform solution of the amine hydrochloride. The filter cake product was washed with chloroform and air dried, wt. 89.9 g. The infrared spectrum of this product showed no ammonium chloride. An aqueous solution of the product was neutral; however, there was a slight indication of chloride ion using a silver nitrate test.

When heated in a capillary tube, gas was evolved at 113° C to form a foam; at 260° C, more expansion occurred and at 280° -300° C, the material softened to a thick syrup with more gas evolution. A thermogravimetric analysis on this material in air from room temperature to 980° C left 18% residue. At 300° C, only 20% of the material had decomposed. Another 30% was lost between 300° and 500° C. There was slightly less weight loss in helium. An elemental analysis of the product was as follows:

    ______________________________________                                                 %           Found                                                      ______________________________________                                                 C           10.17                                                              H           5.61                                                               N           41.04                                                              P           19.06                                                              Cl          1.70                                                       ______________________________________                                    

Treatment of Fabrics

A solution containing the desired weight percent of the flameproofing reagent in sufficient water to just saturate the cloth was poured on a weighed piece of cloth lying flat in a plastic bag. The solution was worked over the surface of the cloth, until it was uniformly wet. After standing for about fifteen minutes, the cloth was placed in an oven at the desired temperature and cured. After curing and drying, the cloth was allowed to equilibrate before being weighed.

Cure Conditions

Cure was effected at 140° C or as shown in the following table using the one operation to also dry the wet sample. Formaldehyde or trimethylolmelamine and quarternary base, sodium hydroxide or magnesium chloride were included as auxiliary treatments in some instances attempting to make the material more durable to washing, and these auxiliary agents are present in the same aqueous solution as the primary reagent when it is applied to the material.

Flammability Tests

Samples of cloth 10 in. × 31/2 in. were clamped in a metal stand and tested according to AATCC Test Method 34-1969 using a propane torch in place of the special gas mixture. This flammability test is described in J. Amer. Assoc. Text. Chem. and Colorists 2 (3), 49/19 (1970).

Tabulation of Data

The test data are tabulated in the following table. The table is divided into three main sections: Fabric Treatment, Flammability Tests and Miscellaneous Conditions. The following column headings are used. The added notes are for explanation of their meanings where not self explanatory.

    ______________________________________                                         Column   Heading      Explanation                                              ______________________________________                                         1      Cloth Type                                                              2      Reagent      * - Melamine/PCl + NH.sub.3 product                        3      Auxiliary    material used to bind to                                                       cloth such as formaldehyde                                                     and catalyst; QB = quarternary                                                 base, TMM = trimethylolmelamine                            4      % Final Add-On                                                                              weight percent of product added                                                to the cloth after all processes                                               including laundering if indicated                                              in column 9                                                5      Distance     this represents the length of                                     Burned, in.  the sample that was burned                                                     out, charred or scorched from                                                  the ignited edge                                           6      Time, Sec    time from ignition to removal                                                  of flame even though self                                                      extinguishment had already                                                     occurred                                                   7      (SE)         answers question --Did the                                        Self Extinguish                                                                             fire self extinguish before                                                    burning the entire sample                                                      length Y = yes; N = no                                     8      Cure Temperature                                                                            temperature at which the                                                       wet cloth was dried and cured                                                  in a single operation                                      9      Post Treatment                                                                              indicates treatment of sample                                                  after curing but before                                                        flammability test. L = laundered,                                              detergent wash and dried;                                                      NL = Not Laundered                                         ______________________________________                                    

    __________________________________________________________________________                                          Miscellaneous                             Fabric Treatment           Flammability Test                                                                        Conditions                                                      %    Distance     Cure                                                         Final                                                                               Burned,                                                                             Time,   Temp.                                                                              Post                               Cloth Type                                                                              Reagent                                                                             Auxiliary                                                                              Add-On                                                                              in.  Sec. SE ° C                                                                         Treatment                          __________________________________________________________________________     cotton        --      0.00 10   1    N  --  NL                                 65/35                                                                          polyester/cotton                                                                             --      0.00 10   1    N  --  NL                                 cotton   *    --      3.27 31/2 3,15 Y  120 NL                                 cotton   *    --      3.27 10   3    N  120 L                                  65/35    *    --      13.2 4    3    Y  140 NL                                 polyester/cotton                                                               65/35    *    --      13.2 10   3    N  140 L                                  polyester/cotton                                                               cotton   *    --      2.5  51/2 12   Y  150 NL                                 cotton   *    --      2.5  10   13   N  150 L                                  65/35    *    --      9.3  6    15   Y  150 NL                                 polyester/cotton                                                               65/35    *    --      9.3  10   15   N  150 L                                  polyester/cotton                                                               65/35    *    CH.sub.2 O                                                                             4.45 10   8    N  120 L                                  polyester/cotton                                                               cotton   *    CH.sub.2 O . Q.B..sup.1                                                                20.3 3    20   Y  130 NL                                 cotton   *    CH.sub.2 O . Q.B.                                                                      14.7 6    15   Y  130 L                                  65/35                                                                          polyester/cotton                                                                        *    CH.sub.2 O. Q.B.                                                                       30.7 3    20   Y  130 NL                                 65/35                                                                          polyester/cotton                                                                        *    CH.sub.2 O . Q.B.                                                                      0    10   15   N  130 L                                  cotton   *    CH.sub.2 O . NaOH                                                                      7.7  10   10   N  140 L                                  65/35    *    CH.sub.2 O . NaOH                                                                      6.45 8    8    N  140 L                                  polyester/cotton                                                               cotton   *    Q.B.    5.7  10   5    N  140 L                                  65/35    *    Q.B.    6.25 10   5    N  140 L                                  polyester/cotton                                                               cotton   *    TMM.sup.2, Q.B.                                                                        6.4  4    5-30 Y  140 L                                  65/35    *    TMM, Q.B.                                                                              8.9  10   5    N  140 L                                  polyester/cotton                                                               65/35    *    TMM, Q.B.                                                                              9.5  10   18   N  140 L                                  polyester/cotton                                                               50/50    *    TMM, Q.B.                                                                              20.0 41/2 3    Y  140 NL                                 polyester/cotton                                                               50/50    *    TMM, Q.B.                                                                              7.6  10   10   N  140 L                                  polyester/cotton                                                               65/35    *    CH.sub.2 O . Q.B.                                                                      3.85 10   8    N  140 L                                  polyester/cotton                                                               65/35    *    TMM, Q.B.                                                                              10.7 10   15   N  140 L                                  polyester/cotton                                                               65/35    *    CH.sub.2 O . MgCl.sub.2                                                                4.86 10   10   N  140 L                                  polyester/cotton                                                               cotton   *    CH.sub.2 O . MgCl.sub.2                                                                7.1  10   10   N  140 L                                  __________________________________________________________________________      *Melamine/PCl.sub.5 + NH.sub.3?                                                SE = Self Extinguishing?                                                       Y = Yes                                                                        NL = Not Laundered                                                             N = No                                                                         L = Laundered                                                                  .sup.1 Quarternary base                                                        .sup.2 Trimethylol melamine                                                    Note:                                                                          Untreated cotton and polyester/cotton cloth are not self extinguishing in      the flammability test and data for these materials are given for               comparison purposes.                                                     

Although the invention has been described in terms of specified embodiments which are set forth in considerable detail, it should be understood that this is by way of illustration only and that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent to those skilled in the art in view of the disclosure. For example, although mixtures of compounds of the invention were used for flameproofing, each individual compound is a flameproofing agent, i.e. each compound whether one, two or all three A's of the general formula is N=P(NH₂). Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention. 

What I claim is:
 1. A process for making flame-retardant material from cotton and polyester-cotton having about 30 to 70% by weight cotton comprising treating said material with an aqueous solution of a mixture comprising compounds of the formula ##STR5## wherein A is NH₂ or N=P(NH₂)₃, provided at least one A is N=P(NH₂)₃ in sufficient amount and curing the treated material at a sufficient temperature to make the treated and cured material self-extinguishing when subjected to a flame sufficient to ignite and consume the untreated material.
 2. A process of claim 1 wherein said material comprises about 65% by weight polyester and 35% by weight cotton.
 3. A process of claim 1 wherein said material comprises about 50% by weight polyester and 50% by weight cotton.
 4. A process of claim 1 wherein said material comprises cotton.
 5. A flame-retardant polyester-cotton material made by the process of claim
 1. 6. A process of claim 1 wherein said solution additionally contains formaldehyde and a quaternary base to make the material more durable to washing.
 7. A process of claim 1 wherein said solution additionally contains trimethylolmelamine and a quarternary base to make the material more durable to washing. 